May 17, 2015 ALP Monthly Meeting Report
by James Kevin Ty
 

Last May 17, ALP held their monthly meeting at Exploreum at SM Mall of Asia in Pasay City.  Members who attended were ALP President James Kevin Ty, wife Charito and son Kendrick Cole KC Ty;  Treasurer Andrew Ian Chan and Iah Serna; Secretary Christopher Louie Lu , wife Karren and daughter Frances; director Edge Lat, Peter Benedict Tubalinal ;  Justine Garcia and Norman Marigza. Guests from UP Astro Soc and RTU Astro Soc members Orville Pelicano, Poly Magaday, Alfred Soriano, Precious Jara Prestosa , Mark Lenczner Mendoza, and Mic Caldo.

Meeting started at around 3:00pm with ALP Secretary Christopher Louie Lu discussion on Spectroscopy. As astronomers, we always look at stars. And there are a variety of stars in the night sky, a mix of different brightness, color & size. But more that these obvious traits, it is also through starlight that we know so much about these beautiful "diamonds in the sky." Unlocking the secret of starlight takes a collection of people with the extraordinary knowhow in various fields of sciences. It was Isaac Newton who first discovered that white light is composed of different  colored light & he called it the 'Spectra'. This was followed by Joseph von Fraunhofer who discover that there are dark lines across the spectra & that these lines are different and distinct from other stars. These dark lines will later be called the "Franhofer Absorption Lines." The partnership of Gustav Kirchoff & Robert Bunsen who discovered the connection between these Absorption Lines with the known chemical elements. Both scientists has successfully figured out how to read these absorption lines and actually know the star's chemical composition. Fr. Angelo Secchi, Jesuit Priest & Astronomer, who made the first classification of stars based on their  color spectra. Henry Drapper who first took photographs of various spectra from different stars. Edward Pickering, who took large number of spectra from a wide field telescope and have each stellar spectra analyzed & cataloged. Employing a staff of women to deal with this monumental task as women was believed to be more patient & thorough in doing them. There are a few women scientists worth noting. Annie Jump Canon, who took Fr. Secchi's spectral classification and improved on it. This method of stellar classification is now being used by astronomers since. Henrietta Swan Leavitt, discovered the relation between the luminosity and the period of Cepheid variable stars. This period/luminosity relationship will be used decades on to measure  the expansion of the universe. Cecilia Payne was able to figure out the color/temperature & hydrogen feul relationship inside a star. Combining this with the classification system by Annie Jump Canon, they were able to tell & estimate the hydrogen feul contents of stars. Data, research and analysis made by these unsung heroines of astronomical science was then gathered and compiled by Ejnar Hurtzprung & Henry Noris Russel to create a diagram that shows the Brightness/Temperature & Size/Color relationship of different stars. This diagram is now known as the "Hurtzsprung-Russel Diagram" & has since became a powerful tool to astronomers to classify different types of stars.

This understanding of the visual spectrum has opened the way for astronomers to understand the greater parts of the invisible spectrum, Gamma, X-ray, Ultraviolet, Infrared, Microwave & Radio wave. Virtually invisible to human eyes, ingenuity & innovation has enabled us to see these various parts of the spectrum. We were able to design, build & send various probes up in our upper atmosphere to continually see the invisible that led to the creation of the Chandra X-ray Probe, the Hubble Space Telescope, the Spintzer & Hechel Infrared Telescopes and the WMAP Microwave Telescope.

Looking forward to the next generation of telescopes is the James Webb Space Telescope which is the successor to the Hubble Space Telescope. This telescope will be bigger and could see farther than its predecessor. It could see well into the visible range but also could see most of the infrared wave spectrum. Expectations for this telescope is very high so all preparations & planning is made very meticulously for it's success. Though this mission is plagued  with delays and budget cuts, scientist, designers & engineers push on to make it on its planned launch date on October 2018.

This was followed by another interesting topic on Measuring Light: Basics of Photometry by ALPer Norman Marigza.
Photometry is the science of measuring light. It is a combination of metrology and optics. Light exists in various forms but photometry's main concern is the measurement of the flux at visual wavelengths. The flux received, combined with measurements from spectroscopy and astrometry will allow us to deduce various properties of the source.

A demo on how to do photometry was presented using the software Iris. Differential photometry (measurements taken at the same image field) was used with the secondary standard star nu Andromedae and compared against other stars in the field through the magnitude equation m1 - m2 = -2.5 log (b1/b2).

Applications on photometry were also described such as: light pollution studies; transit and eclipse events, such as those associated with exoplanets and variable star systems; and limb darkening coefficients to test against stellar atmosphere models. An astronomy program was also introduced entitled "Philippine Light Map" in which the local astronomy community is invited to take part by providing image data to monitor and determine local light pollution levels.

Lastly, ALPer Iah Serna and President James Kevin Ty then invited members to join ALP's May 31, 2015 Excursion at Canyon Cove in Batangas. Meeting ended at around 5pm.

Meeting proper started at 3:00pm	ALPers and guests listen to the interesting lecture topics presented by ALPers Christopher Louie Lu and Norman Marigza.
ALP Secretary Christopher Louie Lu lectures on Spectroscopy.	ALPer Norman Marigza lectures on Measuring Light: Basics of Photometry.